chore(docs): add cookbook/blog link to docs (#2410) [skip ci]

docs/reward_modelling.qmd

@@ -41,6 +41,10 @@ Bradley-Terry chat templates expect single-turn conversations in the following f
 
 ### Process Reward Models (PRM)
 
+::: {.callout-tip}
+Check out our [PRM blog](https://axolotlai.substack.com/p/process-reward-models).
+:::
+
 Process reward models are trained using data which contains preference annotations for each step in a series of interactions. Typically, PRMs are trained to provide reward signals over each step of a reasoning trace and are used for downstream reinforcement learning.
 ```yaml
 base_model: Qwen/Qwen2.5-3B